1. Field
Embodiments of the present disclosure relate to a semiconductor memory technique, and more particularly, to a data storage device and a method of driving the same.
2. Description of the Related Art
Due to increasing demands for portable application devices, such as digital cameras, smart phones, and tablet PCs, and replacement of conventional hard disk drives with solid-state drives (SSDs), markets for non-volatile memory devices are rapidly growing. Among these non-volatile memory devices, NAND flash memory devices are popular due to low manufacturing cost for high degree of integration.
Recently, downscaling the NAND flash memory device with conventional two-dimensional (2D) memory cell array architecture has become more difficult as 20 nm or smaller photolithography techniques have reached their limits. In addition, design issues, which are related to reduction of a sensing margin in accordance with reduction of a number of electrons stored in a data storage film (e.g., a floating gate), and related to disturbances between memory cells, have become barriers against the downscaling of the conventional 2D memory cell array architecture. To address the issues for downscaling the NAND flash memory device, various 3D NAND flash array structures have been suggested.
In the 3D NAND flash array structures, as an I-V curve of memory cells does not have a precipitous slope within a range of operating voltages of the memory cells, threshold voltages Vth of the memory cells exhibit a wide distribution, resulting in a narrow and tight refresh margin for operating a 3D NAND flash memory device. Such a narrow and tight refresh margin may increase a read time of an addressed memory cell of the 3D NAND flash memory device, thereby impeding improvement of an operating speed of the 3D NAND flash memory device. Therefore, in order to enhance an operating speed for a NAND flash memory device, a new mechanism for operating a flash memory device and a suitable memory cell structure for implementing the mechanism are required.